Problem: Expand.
Explanation: We expand the parentheses using the distributive property : $ A(B+C+D)= A\cdot B+ A\cdot C+ A\cdot D$ We can also think about the problem using an area model: $n^2$ $5n$ $6$ $-n^2$ Here's how the solution goes, algebraically: $\begin{aligned} &\phantom{=}{-n^2}(n^2+5n+6) \\\\ &={-n^2}(n^2)+({-n^2})(5n)+({-n^2})(6) \\\\ &=-n^4-5n^3-6n^2 \end{aligned}$ Here's how the solution looks in terms of the area model: $-n^4$ $-5n^3$ $-6n^2$ $n^2$ $5n$ $6$ $-n^2$ In conclusion, $-n^2(n^2+5n+6)=-n^4-5n^3-6n^2$